If you’re a newly signed up customer and want to continue subscribing to the 20 GB for $20 Data Plus option, just leave it on! It will be automatically renewed at the start of each month and added to your monthly bill.
If you no longer want to subscribe to it, make sure that you switch it off before the end of the month. You can do this by heading to your CirclesCare app > Customize > Plus.
The 20 GB for $20 Data Plus option is only available on the $28 /mo Base Plan and $65 /mo +Phone Plan.